Drying apparatus



March 28, 1939. r U A. R. SMITH 2,152,367

' 'DRYING APP-ARATUS Filed April 15, 1938 s Sheets-Sheet 1 INVENTORVfllrm f1. Smzli Q ZL'M.

ATTORNEY March 28, 1 939. AQR. SMITH v 2,152,367

DRYING APPARATUS Filed April 13, 1958 5 Sheets-Sheet 2 INVENTOR XFAZLLLATTORNEY March 28, 1939. R s H 2,152,367

DRYING APPARATUS Filed April 13, 1938 5 sheets-Sheet 3 INVENTOR ATTORNEYPatented Mar. 28, 1939 DRYING APPARATUS Alfred R. Smith, Forest'Hills,N. Y., assignor'to Combustion Engineering Company, Inc., New

York, N. Y.

Application April 13, 1938, Serial No. 201,681

Claims.

' This invention relates to systems i'or drying wet materials and hasfor its purpose the provision of certain improved features in one typeofapparatus used for this purpose. 5 A statement of what the improvedfeatures are will be postponed until a description of the ap paratusgenerally has been given.

In the following specification reference will be made to theaccompanying drawings, the three figures of which showschematicallythree instal lations embodying the invention, Fig. 1 showing it a in oneform, and Figs. 2 and 3 showing it each in a varied form;

Referring first to Fig. 1, the material to be 1| dried is fed into adrying tower I through a pipe 2. Hot gases from the furnace. 3 are ledto the drying tower I through a'pipe connection 5. The

- material to be treated passes downward" through the tower Itogetherwith the drying gases and reaches the disintegrating mill 1where the material is agitated and comminuted and where the principalpart of the drying operation occurs.

' .The mill is driven by any desired means such as the motor 9. Theconmiinuted material together with the drying gases and the moistureevaporated from the material leave the mill 1 and are conducted byconduit I I to the cyclone separator I3. Here the solids are separatedout, collecting at the lowerend of the'cyclone, the gases, substantiallycleared of solids, being carried off through the connection I5, to a fanII, which forces them through duct l9 to a point of disposal.

The solids separated out are taken off through the outlet 2|. ,Rawmaterial for treatment is brought in through the connection 23 from thehopper 24. -The installation illustrated is adapted particularly todrying very wet materials. Such materials present some difliculties inhandling, which 40 difliculties are, in accordance with prior practice,overcome by admixing a certain amountof previously dried material'withthe incoming raw material. In accordance withthis prior practice,theconnection'25 from outlet 2I carries to the (5 mixer 21 the requiredportion of the dried material, the portion, not required beingdischarged through branch 29. Damper3l makes it'possible to dividethedried material in the desired ratio.-

The-dried material is thoroughly mingled with the raw wet material inthe mixer-conveyor 21 and the mixture is discharged by the conveyor 7into pipe 2.

During the evaporation of the moisture, the temperature of the gasesbrought in through pipe 56 5 falls and additional hot gases arecontinuously supplied through the pipe 5. This means that acorresponding amount of gases must be discharged at some point from thesystem. In addition, the moisture evaporated increases the amount ofgases and this excess must also be dis-"- charged. I

The gases to be vented may in some cases be discharged directly to theatmosphere. At 38 is shown a vent to atmosphere for this purpose, the

vent being equipped with damper :4. at the 1b point where the materialis fe'd into the delivery pipe 2, there has heretofore inevitably beensome .leakage of gases. Either air leaks in, in indefinite,

uncontrolled amounts, or gases leak outward from the system making ituncomfortable or 11130551.- 15 ble to work in the vicinity of thefeeding device. Ohe ofthe main objects of my invention is to obviatethis difliculty and this is accomplished by providing means to keep thepressure in the feeding device adjacent'to-the inlet to pipe 2 at 20 orsubstantially at atmosphere. For this purpose I- provide a branchconnection 31 from pipe I 9 to the interior of the casing of mixer 21.

damper I is also provided in pipe 2. b By this provision a numberofadvantageousfeatures are obtained, including the removal of thediihculty mentioned. Primarily, outward leakage can be preventedentirely and at the same time the amount of airleakage into the systemat 30 this point can be minimized. In addition, dust carried by gasesleaving the separator through pipe I 5 is by the improvement partlysaved instead of being lost by discharge into the air or to the furmice.To discharge such dust to the air is usually 5 objectionable and todischarge it to the air or'deliver it to the furnace is wasteful wherethe dust is of any value. To the extent that it is saved and reclaimed,the invention has a beneficial eiIect, in addition to the main one firstmentioned. The 40 arrangement also has the great advantage that it makesit possible, as explained more fully below, to regulate the amount ofhot gases taken from the furnace without having a. damper in pipe 3"through pipe I] and disintegrator l to drying tower l and pipe 2. Onits outlet side, the fancreates a pressure above atmosphere in pipes I9and 31. Obviously. y a proper setting oioamp- 5s,

This branch is equipped with a damper 39 and a ers 39 and 4|, primarilythe former, a pressure equal to atmospheric or slightly above orslightly below, can be obtained in the mixer casing.-

Preferably the pressure is made slightly sub-atmospheric, so that there.is no escape at this point of gases and dust, but only a slight inwardleakage of air. v

To regulate the amount of hot 'gases taken from furnace 3 through pipe5, damper 4| is suitably adjusted. Thus, if the gases coming from thecyclone are too hot, so that their discharge would entail waste ofuseful heat, and it is therefore desired to cut down the hot gas supplycoming from the furnace, damper 4| is moved toward its open position.This will tend to suck in air through the openings from the atmosphereinto the casing 21, and to complete the setting,

damper 39 is also moved far enough toward its.

wide-open position to maintain or to re-establish the slightlysub-atmospheric pressure in the casing 21. Gases will then be drawnaway-faster from l9 and 31, and as a result less gases will be drawn inthrough 5.' Conversely, if the gases from the separator are too cool,dampers 4| and 39 are moved in a direction toward their closed position,thereby causing less gas to be withdrawn from H! and 31 and more to betaken in through 5.

Preferably this adjustment is made automatically, and for this purposethe-following apparatus is provided. At l9 there is arranged the bulbelement 43 of aithermostatic control connected by 45 to the element 41actuating damper 4|. Any suitable thermostatic control may be employed,which will open and close damper 4| by the right amount responsively totemperature variations. in the gases.

To keep the pressure in 21 at the desired point, pressure responsivemeans 5|, subject'to the pressure in 21, are employed, acting throughconnection 49 and actuating means 53 to set the damper 39 to maintainthe desired pressure in 21.

The usual means, such as thermostat 55, controlling the fuel and airsupplied to the furnace, are used to hold the temperature-oi the gasespassing through pipe 5 constant.

, In Fig. 2 isshown a variation of the form of the invention from thatdescribed above. This variation consists in the addition of pipe 6|,branching off from 31 and extending to pipe 5. In this pipe is a damper63 actuated by thermoe static means 65 responsively to temperatures atthe fan outlet. This damper acts like damper 4| described above toregulate the amount of gases taken oh the furnace through pipe 5. In theform of Fig, 1 all the gases, which are to be recirculated, are passedthrough the conveyorrnixer housing. The form of Fig. 2 is used in caseswhere the amount of the recirculated gases is too large for this, orwhere for some-other reason it is undesirable to send all these gasesthrough the casing. The dampers 39 and 4| in pipes 31 and 2 are used asheretofore, but the by-pass 6| takes care of the greater part of therecirculated gases.

In some instances it will be necessary or desir-- able to deodorize allgases before discharging them to the atmosphere.

An arrangement for I this purpose embodying-my invention is shown I inFig. 3. The arrangement is quite similar to that of Fig. 1, but insteadof discharging excess gases to atmosphere by means of vent 33, a connection 33a to the furnace is provided which discharges the gases tosome point in the furnace where the temperature is high enough todeodorize these gases. In the form shown, the gases pass downwardthrough the baflie 61 and are discharged into the furnace at the lowerend of the baiiie. The excess is all ultimately discharged from thestack 69. The amount of gases taken off the furnacethrough 5, and theregulation of the pressure in casing '21 are effected exactly as in theform of Fig. 1.

What I claim is: 1. In apparatus of the kind described, the com-.bination of a drying and pulverizing mill, a

furnace, a duct from the furnace to the mill to supply drying gases, amixing device means to deliver to 'the mixing device raw wet material tobe treated, meansto deliver to the mixing device treated dried materialto be mixed in the mixing device with the raw material, a separator, afan, a duct carrying the mixed material from the mixing device to themill, a duct to convey the gases and material from the mill to theseparator, means to conduct the gases from the separator to the inlet ofthe fan, a duct from the outlet of the fan to the mixing device, dampermeans in the duct to the mixing device, and damper means in the ductfromthe mixing device, where'- by the pressure in the mixing device canbe adjusted to a point differing slightly from atmosphere.

2. Apparatus in accordance with claim 1, and. further comprising meansautomatically adjusting the position of the damper in the duct leadingto the mixer responsively to pressure changes in the mixer, to keep suchpressure slightly below atmospheric. 3. Apparatus in accordance withclaim 1, and further comprising means automatically adjustthe positionof the damper in the ,duct leading from the mixer to temperaturechangesin the gases coming from thefan.

5. Apparatus in accordance with claim 1, and further comprising meansresponsive to pressure conditions in the mixing device to open furtherthe damper in the duct leading to the mixing device when the pressure inthe mixing device falls below a predetermined point, and to move'it in aclosing direction when such pressure falls below a predetermined point,and means respon-- sive to temperature conditions of the gases lea-v ingthe fan to move the damper in the duct leaving the mixing device in .anopening direction when said temperature falls below a predeterminedpoint, and to move it in a closing dlrec-' a predetermined point.

tion when it rises above ALFRED B. SMITH,

, ing the position of the damper in the duct lead-

